GB1250289A - - Google Patents

Abstract

1,250,289. Master cylinders. ALFRED TEVES G.m.b.H. 20 Feb., 1970 [25 Feb., 1969], No. 8278/70. Heading F2F. An hydraulic brake actuating system for motor vehicles with a master cylinder 1 comprising an actuating piston 9 and a booster piston 10, includes a booster pump 2 supplying pressure medium to a chamber 21 behind the booster piston 10, the working pressure of the pump acting upon the piston 10 being controlled by the relative movement of a control piston 19 with respect to a control sleeve 20 which together constitute a throttle 38; the piston 19 and sleeve 20 are provided with abutments for limiting relative movement between them and the sleeve is slidably guided on the piston. As shown, a sleeve 13 divides the bore 8 of the housing 7 into chambers 11, 12 connected to brake operating circuits via ports 39, 40, the sleeve being retained in position by a spring- loaded ball 14 and having a limited displacement so that pressure differences in the chambers can be balanced. In a braking operation, the control device 18 comprising the piston 19 and sleeve 20 is displaced inwardly against the force of springs 33, 34, the throttle 38 remaining open and fluid pressure is transmitted to ports 39, 40 and the wheel brake cylinders until the pressure in chambers 11, 12 exceeds the counteracting force of spring 32 when the fluid passage at the throttle is reduced until the sleeve 20 closes the passage; a rise of pressure in the chamber 21 acts on the booster piston 10 and force is transmitted to the actuating piston 9; when the input actuating force applied to the piston 19 is reduced, the throttle 38 is reopened and full pressure of the pump 2 circulates. An excess pressure valve 25 incorporated in the piston 19 opens under very high input forces and establishes re-circulation of fluid medium to the tank 3.